Uploaded November 2024 | Updated September 2026, 3 weeks ago

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Finalized tuning on one of the circuits I made based around Steve Ward's designs. This one easily wants to pull over 12A at only 30V or less with a certain coupling and gate bias so I back that down to about 3.5V using the pot. With a tiny drop of glass on the breakout point the arc can easily hit about 7-8 inches at 60V/600W. That's actually about all I really want from one of these but since it only had about 300V on the drain I could probably push this one to ~100VDC no problem. Without the glass, the soldering iron tip electrode is no longer viable beyond about 500W.

(You can see this tuning is based around feeding the circuit with a DC supply which is switching at much higher frequency than line voltage, so don't expect similar results with a mains AC input unless you have ridiculous smoothing.)


UJ4C075033K4S SiC fet
100pF 7.5kV RF ceramic doorknob + primary 6 turns
(10AWG 7.5cm wide x 8.5cm tall)
16AWG secondary
(3cm wide x 3.5cm tall)
100pF Cds
12nF Cgs
4.7ohms gate resistance (2S2P 1W 4.7ohm metal film resistors)